Comparison of the Effects of Vitamins and/or Mineral Supplementation on Glomerular and Tubular Dysfunction in Type 2 Diabetes

Abstract

OBJECTIVE -The present study was designed to assess the effect of magnesium plus zinc, vitamins C plus E, and a combination of these micronutrients on nephropathy indexes in type 2 diabetic patients.RESEARCH DESIGN AND METHODS -In a randomized, double-blind, placebocontrolled clinical trial, 69 type 2 diabetic patients were randomly divided into four groups, each group receiving one of the following daily supplement for 3 months: group M (n ϭ 16), 200 mg Mg and 30 mg Zn; group V (n ϭ 18), 200 mg vitamin C and 100 IU vitamin E; group MV (n ϭ 17), minerals plus vitamins; and group P (n ϭ 18), placebo. Urinary albumin excretion and N-acetyl-␤-D-glucosaminidase activity (NAG) in urine were determined at the beginning and at the end of the trial. Treatment effects were analyzed by general linear modeling. RESULTS-Results indicate that after 3 months of supplementation, levels of urinary albumin excretion decreased in the V and MV groups (P ϭ 0.034 and P ϭ 0.005, respectively). Urinary NAG activity did not significantly change in any treatment groups. Levels of systolic, diastolic, and mean blood pressure significantly decreased in the MV group (P ϭ 0.008, P ϭ 0.017, and P ϭ 0.009, respectively). Also, combination of vitamin and mineral supplementation had significant effects in decreasing fasting serum glucose (P ϭ 0.035) and malondialdehyde concentrations (P ϭ 0.004) and in increasing HDL cholesterol and apolipoprotein A1 levels (P ϭ 0.019). There was no significant change in the levels of these parameters in the other three groups.CONCLUSIONS -In conclusion, the results of the present study provide evidence for the effects of vitamins C and E and also combination of magnesium, zinc, and vitamins C and E supplementation on improvement of glomerular but not tubular renal function in type 2 diabetic patients. Diabetes Care 28:2458 -2464, 2005D iabetic nephropathy is a serious complication of diabetes and a major cause of mortality and morbidity in these patients (1,2). Results of studies in animal models and humans have demonstrated that diabetes is associated with oxidative stress (3-5) and reduced levels of antioxidants (6). It has been well established that plasma magnesium levels in patients with diabetes is somewhat decreased (7,8). Numerous studies have found decreases in physiological measures of zinc status, hyperzincuria, and indications of zinc malabsorption in diabetic individuals (7,9). Levels of plasma ascorbic acid were found to be significantly lower in diabetic patients compared with nondiabetic control subjects in most studies (10 -12). Based on their results, the researchers observed that individuals with diabetes have significant defects of antioxidant protection, which may enhance their susceptibility to oxidative stress (12).Oxidative stress is hypothesized to play an important part in the development of late diabetes complications (6). Chronic hyperglycemia increases oxidative stress and considerably modifies the structure and function of proteins and lipids, due to glycoxidation and peroxidation...

Effect of Zinc Supplementation on Microalbuminuria in Patients With Type 2 Diabetes: A Double Blind, Randomized, Placebo-Controlled, Cross-Over Trial

“…Unfortunately, there are few studies in this field, which contain some controversial results. In one trial, using a combination of zinc and magnesium, a decreased urinary albumin excretion was observed without any significant effect on blood pressure or lipid profiles [11]. Another study found that intake of zinc and melatonin for three months reduced plasma lipid concentrations and urinary albumin excretion [12].…”

“…The placebo capsules contained 30 mg of lactose and were made to appear the same as the zinc capsules, in size, shape and color. The prescribed zinc dosage was based on the method used in other studies [11,14].…”

Grape seed extract and Zinc containing nutritional food supplement delays onset and progression of Streptozocin-induced diabetic cataract in Wistar rats

“…Studies suggest that Zinc prevents diabetes-induced GSH loss in the retina (Moustafa 2004), vitamin C and E prevents inhibition of glutathione peroxidase, glutathione reductase and superoxide dismutase activities in retina (Mustata et al 2005;Kowluru et al 2001;Penn et al 2008). Increased oxygen free-radical production lowers the intracellular magnesium concentration and in light of such evidence, vitamin E administration might also regulate the intracellular magnesium concentration (Farvid et al 2005). A synergistic effect of vitamins C and E along with Zinc could be expected based on the different environments in which they act (Farvid et al 2005).…”

“…Increased oxygen free-radical production lowers the intracellular magnesium concentration and in light of such evidence, vitamin E administration might also regulate the intracellular magnesium concentration (Farvid et al 2005). A synergistic effect of vitamins C and E along with Zinc could be expected based on the different environments in which they act (Farvid et al 2005). Vitamin C acts in the hydrophilic milieu, scavenging reactive oxygen species, zinc located in the interphase of the bilayer prevents iron or copper binding to the membrane and alpha-tocopherol in the hydrophobic domains of the bilayer inhibits the lipid oxidation free-radical chain reaction (Farvid et al 2005).…”

“…A synergistic effect of vitamins C and E along with Zinc could be expected based on the different environments in which they act (Farvid et al 2005). Vitamin C acts in the hydrophilic milieu, scavenging reactive oxygen species, zinc located in the interphase of the bilayer prevents iron or copper binding to the membrane and alpha-tocopherol in the hydrophobic domains of the bilayer inhibits the lipid oxidation free-radical chain reaction (Farvid et al 2005). Magnesium inhibits Malondialdehyde (MDA) formation in endothelial cells and low Magnesium oxide induced lipid peroxidation (Farvid et al 2005).…”